This invention relates to a distortion-compensated differential circuit which comprises a differential stage comprising a first and a second transistor whose emitters are coupled by a first impedance, and input terminals for an input signal source, and which also comprises a distortion compensation circuit comprising in series between the emitter of the first transistor and a first current source, a first diode as well as the main current path of a third transistor, and also comprising, in series between the emitter of the second transistor and a second current source, a second diode as well as the main current path of a fourth transistor, which third and fourth transistors have their respective bases and collectors interconnected and have their emitters coupled by a second impedance.
Such a differential circuit is known from U.S. Pat. No. 4,682,098 in the form of a voltage-current converter comprising a voltage source V, the first impedance being constituted by a resistor which converts said voltage into a current which is amplified by a translinear circuit comprising four transistors. The first and the second transistor have their collectors as well as their bases interconnected. In order to compensate for conversion non-linearity caused by the non-linearity of the emitter resistance of the first and the second transistor, U.S. Pat. No. 4,682,098 couples a resistor of the same value as the first resistor between the emitters of the third and the fourth transistor.
This compensation provides very remarkable results in the case of small signals.
However, in particular in the case of flash-type fold and interpolation analog-to-digital converters, there is a need to provide compensation over a very wide dynamic range, up to levels of several volts at the output of a differential amplifier.